When beginners talk about engraving quality, most focus on speed and power. But in real-world diode laser use, many “uneven,” “striped,” or “muddy” engravings are not caused by either.
They’re caused by density.
In LightBurn and similar software, that density is controlled by DPI or Line Interval—two terms that describe the same physical behavior in different ways. Understanding how they work (and when they matter more than power) is a major turning point in getting consistent engraving results.
This guide explains what DPI and Line Interval actually do, why they behave differently on different materials, and how to use them correctly—without turning everything into a slow, burned mess.
DPI and Line Interval Are the Same Thing
Let’s clear up the biggest confusion first.
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DPI (Dots Per Inch) describes how many engraving lines or dots are packed into one inch.
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Line Interval describes the distance (in mm) between those same lines.
They are simply two ways of expressing engraving density.
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Higher DPI = smaller Line Interval = denser coverage
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Lower DPI = larger Line Interval = looser coverage
In LightBurn, Line Interval is preferred because it directly reflects machine motion and is easier to control precisely. Changing one automatically affects the other.
👉 You only need to manage one of them.
What DPI / Line Interval Actually Controls
DPI and Line Interval do not control laser strength. They control how completely the surface is covered.
Specifically, they affect:
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Engraving darkness and depth
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Surface uniformity (banding vs smooth fills)
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Detail retention in photos and gradients
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Total engraving time
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Heat accumulation across the material
This is why two jobs with the same speed and power can look completely different if their line spacing is different.
Why “Too Light” and “Too Dark” Are Often Density Problems
Many users respond to light engravings by increasing power or slowing speed. That works—sometimes. But it also introduces new problems like burning, edge charring, or melted acrylic.
Often, the real issue is that the laser simply isn’t hitting enough of the surface.
Increasing density (smaller Line Interval) allows you to:
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Keep power moderate
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Maintain reasonable speed
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Achieve darker, more even fills
This is especially important on materials where heat spreads easily, such as plywood, bamboo, leather, and acrylic. To check the details, you could read the passage below:
Practical Density Ranges (Diode Lasers)
These are safe, commonly used starting points, not fixed rules.
Typical Line Interval Values
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0.05 mm – Extremely dense, very slow, high heat
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0.08–0.1 mm – Balanced, most common for diode engraving
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0.12–0.15 mm – Faster, lighter engraving
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0.2 mm+ – Draft quality, visible scan lines
For most diode laser users:
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10W diode: 0.1 mm is a reliable baseline
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5W diode: 0.08–0.1 mm often works better due to lower energy per pass
Instead of immediately increasing power, try reducing line interval slightly and re-run the job.
Material Behavior: Why One Setting Doesn’t Fit All
A key insight from community testing (and often misunderstood by beginners) is that dot size changes depending on the material, even with the same lens and focus.
Hard, reflective, or glazed surfaces may produce:
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Smaller dots
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Less thermal spread
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Higher apparent resolution
Porous or fibrous materials (wood, paper, leather) often show:
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Larger burn halos
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Dot merging at higher density
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Greater sensitivity to focus height
This is why photo engravings that look perfect on coated tile may look overburned on cardstock at the same DPI.
The takeaway: Density must be adjusted per material, not per image.
DPI, Photos, and Image Modes
For photo engraving, density interacts with image mode:
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Grayscale
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Dither (Jarvis, Stucki, Floyd-Steinberg)
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Newsprint
Higher DPI does not automatically mean better photos.
If line spacing is tighter than your effective dot size, dots overlap and you lose contrast. This is why many experienced engravers prefer moderate density with correct dithering, rather than ultra-high DPI.
Rule of thumb:
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Photos benefit from consistency, not maximum density.
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Clean dots beat crushed tones.
Common Beginner Mistakes with DPI / Line Interval
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Running ultra-tight line intervals with slow speed → Excess heat, dark edges, muddy fills
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Using photo DPI values for vector fills → Unnecessary engraving time
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Assuming DPI = quality → Quality comes from balance, not density alone
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Never changing density between materials → Inconsistent results across projects
How DPI / Line Interval Fits Into the Bigger Picture
Think of engraving quality as a system:
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Power controls how strong each pulse is
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Speed controls how long the laser stays
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Line Interval / DPI controls how completely the area is covered
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Passes control energy accumulation over time
When engraving looks wrong, density should often be checked before power.
When to Adjust Density First
Adjust Line Interval first if:
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Engraving looks striped or uneven
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Surface is too light but edges are already dark
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Increasing power causes burning instead of clarity
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Photos lack smooth gradients
Adjust speed or power first if:
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Engraving is uniformly too shallow
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Material is not reacting at all
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Cutting performance is insufficient
DPI and Line Interval don’t make your laser stronger—but they determine how effectively that strength is applied.
Once you understand density as a coverage tool rather than a resolution gimmick, engraving quality becomes far more predictable. Most experienced users rely on moderate power, reasonable speed, and well-chosen line spacing rather than extreme settings.
Mastering this relationship is one of the fastest ways to move from “it works sometimes” to consistent, professional-looking results.
FAQ
Can I use the same DPI or line interval for all materials?
No. Softer materials like leather and paper often need wider line intervals, while harder materials like wood or coated acrylic benefit from tighter spacing for detail.
Is DPI the same as line interval?
No. DPI is a calculated resolution value, while line interval is a direct mechanical setting. Many laser users prefer line interval because it provides more predictable, repeatable results across different machines and materials.
Which matters more: DPI or line interval?
For most diode and CO₂ laser engravers, line interval matters more. It directly affects dot overlap, engraving depth consistency, and surface texture, while DPI is often just a converted value in software.
Does higher DPI always mean better engraving quality?
No. Higher DPI can cause overburning, muddy details, and longer run times if the laser’s dot size cannot physically support that resolution. Matching DPI or line interval to your actual dot size is more important.
What line interval is best for photo engraving?
Common starting points are:
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0.1 mm for wood and coated materials
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0.08–0.12 mm depending on laser spot size and focus Final results vary by material and lens, so test grids are strongly recommended.
How do I choose between DPI and line interval in LightBurn?
If possible, set engraving resolution using line interval (mm) instead of DPI. This avoids confusion and ensures your settings reflect real mechanical movement rather than software conversions.
